1. Field of the Invention
The present invention relates to a granulate which absorbs water particularly well and further transports water into the interior, thus leading in part to a volume increase, so that the granulate is suitable as a disintegrating agent for pressed molded bodies, such as tablets.
2. Discussion of the Background
Disintegrating agents for tablets or granulates are auxiliary substances which accelerate the disintegration of tablets or of the granulate on contact with liquids, especially water. The purpose is to bring about and accelerate both the disintegration of tablets into coarse fragments and then also disintegration into smaller particles.
Numerous inorganic and organic substances are known as disintegrating agents for tablets, examples including inorganic substances such as bentonites as well as per salts, acetates, alkali metal carbonates/bicarbonates and citric acid. The known organic compounds include starch, modified starch and starch decomposition products, cellulose, cellulose ethers such as methylcellulose, hydroxypropylcellulose and carboxymethylcellulose, poly(meth)acrylates, polyvinylpyrrolidone and cross-linked polyvinylpyrrolidone, alginates, gelatins and pectins.
In the case of tablets pressed from precompounded mixes, the need exists to accelerate disintegration into the original compounds and then also into individual constituents.
In the case of tablets pressed from non-precompounded mixes, the density achieved during pressing is frequently very high, and on contact with water it delays the desired disintegration of the tablets. This is often undesired, because constituents then dissolve only after a delay.
WO 98/40463 describes a disintegrating agent granulate and use thereof in molded bodies such as tablets having detergency or cleaning activity, where the granulate has a high adsorption capacity for water as well as a particle size distribution in which at least 90 wt % of the particles have a size of at least 0.2 mm and at most 3 mm. The granulate contains preferably 25 to 100 wt % of disintegrating agent such as starch, starch derivatives, cellulose, cellulose derivatives, alginic acid, carboxymethylamylopectin, polyacrylic acid, polyvinylpyrrolidone and polyvinylpolypyrrolidone. According to this publication, the presence of anionic or nonionic surfactants has an adverse effect on tablet disintegration time. The granulate is manufactured by a conventional method such as spray drying, superheated steam drying of aqueous formulations, or by granulation, tableting, extrusion or roll-compacting of powdered constituents.
A process for manufacture of detergent or cleaning agent tablets is described in WO 96/06156. Citric acid or citrates, bicarbonates and carbonates, bisulfate and percarbonate, microcrystalline cellulose, sugar, sorbitol or swellable layer silicates of the bentonite or smectite type are cited as disintegrating agents. The disintegrating agents are used in proportions of 1 to 25 wt % in the form of individual raw material or as compounds.
German Patent Application A 4404279 describes the following disintegrating agents for detergent or cleaning tablets: starch, starch derivatives, cellulose, cellulose derivatives, microcrystalline cellulose, salts of polymeric polyacrylates or polymethacrylates, methylcelluloses, hydroxypropylcelluloses or methylhydroxypropylcelluloses. Acetates or percarbonates are also cited as disintegrating agents. The applied proportions are as high as 15 wt %. Since water-soluble silicates are used as builders, even proportions as low as 1 wt % can lead to very good results with a combination of poly(meth)acrylates and nonionic cellulose ethers.
In European Patent Application EP 0846756 A1, tablet disintegrating agents are incorporated into the tablets and preferably into the outer solid shell of the tablets.
Combinations of soluble acids and alkali metal carbonates are preferably used. Further possible disintegrating agents can be found in the "Handbook of Pharmaceutical Excipients" (1986). Cited as examples are: starch (modified starch, sodium starch gluconates), gums (agar, guar and others), cellulose, carboxymethylcellulose, alginates, silicondioxide, clay, polyvinylpyrrolidone, polysaccharides and ion-exchange resins.
From European Patent Application EP A 0522766 there are known detergent tablets which contain disintegrating agents functioning according to four different mechanisms: swelling, porosity/capillary effect, deformation and chemical reaction. Described are starch, starch derivatives, carboxymethyl starch, sodium starch glycolates, cellulose and cellulose derivatives, carboxymethylcellulose, cross-linked modified cellulose, microcrystalline cellulose and various organic polymers such as polyethylene glycol, and cross-linked polyvinylpyrrolidones and inorganic swelling agents such as bentonites. Also described are combinations of organic acids and bicarbonates or carbonates of alkali metals.
European Patent Application EP 0628627 A1 describes a water-soluble, water-softening builder in the form of a tablet, in which combinations of citric acid and/or partly neutralized polymers and carbonate and/or bicarbonate or an insoluble polyvinylpyrrolidone are used as disintegrating agents.
European Patent Application (EP 0799886 A2) describes detergent tablets which can contain starch derivatives, cellulose compounds, polyvinyl-pyrrolidone compounds, polyvinylpolypyrrolidone compounds, bentonite compounds, alginates, gelatins and pectins as disintegrating agents. Addition of a polyfunctional organic carboxylic acid such as maleic acid, malic acid, citric acid or tartaric acid together with carbonates or bicarbonates is recommended for further improvement of dissolution time.
Available compositions do not contain any known disintegrating agent which is characterized by nonlinear swelling kinetics, and nowhere is there mentioned the use in disintegrating agents of surfactants, preferably gel-forming surfactants or surfactants which are thickened with water. Heretofore the prolongation of tablet disintegration time by certain surfactants has been described as a disadvantage.